Metano em áreas inundáveis amazônicas com águas negra, clara e branca: potencial de produção pela microbiota e modelagem matemática

Abstract

This thesis evaluated the effect of flooding on the metabolic response of soil microbiota in Amazonian floodplains with black, clear and white waters, and assumed the temperature increase estimated by the Intergovernmental Panel on Climate Change for the Amazon region, in order to evaluate the methanogenic potential and understand the microbial metabolic response under conditions of high CH4 production in these environments. For this purpose, three different studies were designed and developed in forest and agricultural sites of floodplains with black (Negro River), clear (Tocantins River) and white (Solimões River) waters in the Brazilian Amazon, which are presented after the introductory part, Chapter 1. The Chapter 2 evaluated the metabolic capacity of soil microorganisms based on carbon consumption patterns and derived indices obtained from the BIOLOGTM EcoPlate technology. The results of this study showed a difference in the metabolic richness of microbial communities present in white water river floodplain soils compared with those revealed for black and clear water river floodplain soils, whose data variation was explained mainly by water coloration. In turn, Chapter 3 reported the potential for CH4 production by the microbiota present in the same soils evaluated in the first study of the thesis. Methanogenic precursor substrates of the acetoclastic, hydrogenotrophic, and methylotrophic pathways were added to the soil in biological reactors and incubated in the laboratory using the field soil collection temperature plus 2 °C predicted for the Amazon region as an effect of climate change. DNA microarray technique (Geochip v. 5.0S) was used to evaluate microbial functional genes associated with carbon degradation and fixation and methanogenesis. Hybridizations were performed from genomic DNA isolated from the soils with the highest CH4 productions in the incubations, resulting from the conversion of methanogenic substrates (sodium acetate, sodium formate, glucose and methanol) into CH4 . The results of this study revealed that the higher CH4 productions obtained in biological reactors were not associated with higher percentages of hybridizations of genes associated with carbon degradation and fixation and methanogenesis. Finally, Chapter 4 was developed using metadata set composed of soil physical and chemical factors, quantitative molecular abundance data of methanogenic and methanotrophic taxonomic groups from Amazonian floodplains, and landscape metrics to obtain models for predicting CH4 in floodplains of black, clear, and white water rivers. This study represents the first effort to estimate CH4 fluxes using microbiological variables from Amazonian floodplain soils.